This disclosure relates generally to the field of magnetic gears to provide a torque transmission connection between a source of rotational energy and an instrument disposed in a wellbore that requires rotational energy at a different speed and torque than provided by the source.
U.S. Pat. No. 7,549,467 issued to McDonald et al. describes a wellbore rotational instrument system disposed in a wellbore. Rotational energy is supplied by power from a source external to the wellbore or within the wellbore. The system includes a magnetic gear member rotationally coupled at an input thereof to an output of the rotational energy source, and a rotational load, such as a pump coupled at its input to an output of the magnetic gear member. For certain wellbore instruments, such as electrically submersible pumps (ESPs) it is sometimes desirable to use a high speed, low torque electric motor in the wellbore and a low-speed, high torque pump, such as a progressive cavity pump. Other configurations may require the reverse arrangement of speed and torque of the rotating load with respect to those of the rotational energy source. Configuring a magnetic gear member for such applications as proven challenging. It is desirable to have a reliable magnetic gear for use with certain types of wellbore instruments.